MTW Box 21.1 - What can "add and subtract" do for Equation (12)?

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TerryW
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Homework Statement
Derive Equation (15) from Equation (12)
Relevant Equations
See attachment
I haven't posted for a while and I am still (!) working through some of the things I didn't quite get in MTW Chapter 21.

Here is my latest puzzle.

I want to work out how to get from Equation (12) in the attachment, to Equation (15).

I've tried the "add and subtract" ##\{\frac {(-g)^{\frac12}F^{i0}}{4\pi}A_0\delta t\}_{,i}##

This gives me ##+\{\frac {(-g)^{\frac12}F^{i0}}{4\pi}\delta t\}A_{0,i}## and -##\{\frac {(-g)^{\frac12}F^{i0}}{4\pi}\delta t\}A_{i,0}##

Plus ## \{\frac {(-g)^{\frac12}F^{i0}}{4\pi}\}_{,i}A_0\delta t## and minus ## \{\frac {(-g)^{\frac12}F^{i0}}{4\pi}\}_{,i}A_0\delta t##

All this does is allow me to replace ##\{\frac {(-g)^{\frac12}F^{i0}}{4\pi}A_{i,0}\}## with ##-\{\frac {(-g)^{\frac12}F^{i0}}{4\pi}A_{0,i}\}## which I could have done anyway by index manipulation,

I can then add the two versions of (12) to give a new equation which is $$2\delta S = \int \big[ 2\frac {(-g)^{\frac12}F^{i0}}{4\pi}\delta A_{i}+\{\frac {(-g)^{\frac12}F^{i0}}{4\pi}A_{i,0}-\frac {(-g)^{\frac12}F^{i0}}{4\pi}A_{0,i}\}\delta t -2\mathfrak L\}\big]d^3x$$

What this means is that my result for ##\frac {\delta S}{\delta \Omega}## contains the term ##2F^{i0}(A_{i,0} - A_{0,i})## instead of ##4F^{i0}(A_{i,0} - A_{0,i})##

I then had a look at the Plus and Minus ## \{\frac {(-g)^{\frac12}F^{i0}}{4\pi}\}_{,i}A_0\delta t## terms which I had discarded earlier as they cancel, to see if I could find some extra terms, but I couldn't find anything to fix the problem.

Can anyone point out what I am missing?
RegardsTerryW
 

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Hi Terry, I don't think if you remember my other handle though I hadn't forgotten you queries from MTW I did purchase the paper black version from Amazon.com quite a Heavy lifting.

But I'll get there eventually.
Nowadays I am reading Information Theory by Cover and Thomas for my last degree, hopefully I'll achieve it.
Cheers mate, you'll never be forgotten!
 
I mean it is paperback.
 
billtodd said:
Hi Terry, I don't think if you remember my other handle though I hadn't forgotten you queries from MTW I did purchase the paper black version from Amazon.com quite a Heavy lifting.

But I'll get there eventually.
Nowadays I am reading Information Theory by Cover and Thomas for my last degree, hopefully I'll achieve it.
Cheers mate, you'll never be forgotten!
Best of luck with MTW. Should you ever need a steer with any of the problems (I'm currently on Chapter 23), just drop me a message.

CheersTerry W
 
TerryW said:
Best of luck with MTW. Should you ever need a steer with any of the problems (I'm currently on Chapter 23), just drop me a message.

CheersTerry W
We ain't getting younger, but with no Guts no Glory:
 
BTW what was your 'other handle'?
 
TerryW said:
BTW what was your 'other handle'?
Let's just say I am a 21st century polymath... :oldbiggrin:
 
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